The present invention was created to achieve the object of the present invention as described above, a stage portion on which a specimen plate on which blood to be diagnosed is mounted for diagnosis of disease infection； A light irradiation unit positioned below the stage unit and irradiating diagnostic light to blood located at a diagnostic position among blood smeared on a sample plate； An image acquiring unit positioned above the light irradiating unit and acquiring a diagnosis target image of blood for a portion irradiated with light by the light irradiating unit on blood smeared on a specimen plate； Located between the stage unit and the image acquisition unit, the image acquisition unit has a first magnification lens unit having a first magnification to obtain a diagnosis target image having different magnifications, and a second magnification lens having a second magnification greater than the first magnification. An optical system including a portion； A horizontal moving unit horizontally moving the stage unit on which the sample plate is seated so that the image acquisition unit acquires a diagnosis target image for blood smeared on the sample plate； Sample for performing the primary image acquisition process for acquiring the low-magnification diagnosis target image through the first magnification lens unit and the secondary image acquisition process for acquiring the high magnification diagnosis target image through the second magnification lens unit after performing the primary image acquisition process Disclosed is a blood diagnostic device comprising a control unit for performing focusing by controlling a focal length of an optical system for blood smeared on a plate.본 발명은 상기와 같은 본 발명의 목적을 달성하기 위하여 창출된 것으로서, 질병감염여부의 진단을 위한 진단 대상 혈액이 도말된 검체 플레이트가 안착되는 스테이지부와； 스테이지부의 하측에 위치되어 검체 플레이트에 도말된 혈액 중 진단위치에 위치된 혈액에 진단광을 조사하는 광조사부와； 광조사부의 상측에 위치되어 검체 플레이트에 도말된 혈액 중 광조사부에 의하여 광이 조사된 부분에 대한 혈액의 진단대상이미지를 획득하는 이미지획득부와； 스테이지부 및 이미지획득부 사이에 위치되어, 이미지획득부가 서로 다른 배율의 진단대상이
